Re: [RFC/PATCH] Make powerpc64 use __thread for per-cpu variables

Segher Boessenkool
2006-05-10T23:17:58Z

>>> How do you plan to address the compiler optimizing
>> ...
>>> Across the schedule, we may have changed cpus, making the cached
>>> address invalid.
>>
>> Per-cpu variables need to be accessed only with preemption
>> disabled. And the preemption enable/disable operations
>> provide a compiler memory barrier.
>
> No, Richard has a point, it's not the value that is the concern, it's
> the address, which gcc could assume is still valid after a barrier.
> Drat.

Would an asm clobber of GPR13 in the schedule routines (or a wrapper
for them, or whatever) work?

Segher